1. Field of the Invention
This invention relates to an electron beam collector for transit time tubes, in particular traveling wave tubes, having a plurality of metallic electrodes which surround the electron beam and which are spaced from one another by insulating bodies.
2. Description of the Prior Art
In collector which are subjected to a high thermal load and which are electrically insulated from their environment, it is of particular importance to discharge the heat loss developed during the operation of the tube to a sufficient extent in order to avoid breaks in power or even complete breakdowns. If the collectors are of multi-stage design, the heat discharge becomes particularly difficult since the electrodes are additionally also separated from one another by insulating bodies which, naturally, are poor heat conductors and promote a non-uniform heat distribution along the surface of the collector.
In fact, in a multi-stage collector it would be particularly desirable to achieve a good transition of heat between the individual electrodes as the quantity of heat converted in the individual collector stages is also very sensitive to the modulation of the tube and, therefore, the electrodes are exposed to fluctuating thermal loads which change in shock-like fashion and which rapidly lead to impermissably high local temperature gradients.
A multi-stage collector of typical construction is disclosed in U.S. Pat. No. 3,368,104. In this design, the individual electrodes are separated by a stack of insulating rings, stack upon one another with interlying flexible metal layers. The metal layers are extended out of the stack and are connected either directly to the electrodes or, via another, likewise flexible flange. The insulating rings themselves are not secured to the electrodes because of the differing heat expansion. It is readily apparent that in collectors of this type of construction, the heat transport capacity between the individual electrode stages, and also the heat emission to the outer surface of the collector is not favorable. To this may also be added the fact that the construction is extremely fragile, since the electrodes are held in position only by the flexible metal layers. The electrodes cannot be allowed to be exposed to mechanical load, and in particular not to vibrations. Finally, the aforementioned metal layers generally consist of magnetic materials, for example "Kovar", which is also a poor heat conductor and which has a heat expansion behavior that corresponds approximately to that of aluminum oxide or beryllium oxide. Magnetic disturbances of the electron beam should be avoided, however, without fail in the region of the collector.
In order to increase mechanical stability and the heat discharging capacity other structures have been devised. If one refers to U.S. Pat. No. 3,662,212, in particular to FIG. 3, it will become apparent that it is known to totally surround the individual collector stages with an inherently stable pile of ceramic rings stacked one upon another with interposed copper ribs, where the ribs lead alternately to the electrodes and to the casing. However, even in this somewhat expensive arrangement, the heat exchange between the individual electrodes, which fundamentally takes place only along the ribs, is still not satisfactory.
Also, as will be discussed below, it is known in the art to utilize non-deformable clamping rings in collector structures, such as disclosed in U.S. Pat. No. 3,586,100.